Structural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential

Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features.In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels.The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no correlation between ζ-potential and SAR values after immobilization was observed.Our data show that immobilization of MNP, independent of their physicochemical properties, can distinctly affect their SAR. Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues. This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.     

Chemical and magnetic functionalization of graphene oxide as a route to enhance its biocompatibility

The novel approach for deposition of iron oxide nanoparticles with narrow size distribution supported on different sized graphene oxide was reported. Two different samples with different size distributions of graphene oxide (0.5 to 7 μm and 1 to 3 μm) were selectively prepared, and the influence of the flake size distribution on the mitochondrial activity of L929 with WST1 assay in vitro study was also evaluated. Little reduction of mitochondrial activity of the GO-Fe₃O₄ samples with broader size distribution (0.5 to 7 μm) was observed. The pristine GO samples (0.5 to 7 μm) in the highest concentrations reduced the mitochondrial activity significantly. For GO-Fe₃O₄ samples with narrower size distribution, the best biocompatibility was noticed at concentration 12.5 μg/mL. The highest reduction of cell viability was noted at a dose 100 μg/mL for GO (1 to 3 μm). It is worth noting that the chemical functionalization of GO and Fe₃O₄ is a way to enhance the biocompatibility and makes the system independent of the size distribution of graphene oxide.     

Preparation of hierarchical leaf-like cobalt and enhanced magnetic properties by a new low-temperature synthesis method

Hierarchical leaf-like cobalt materials have been synthesized by a simple method at relatively low temperature. The product was characterized by means of XRD, SEM, EDS, and VSM techniques. The effects of temperature and cobalt acetate amount on the final Co were investigated by a series of experiments. It was found that the temperature played an important role in the formation of such novel leaf-like cobalt. When the reaction temperature of the mixture was as low as 40–65 °C, the morphology of final products can be changed from fluffy like to leaf like hierarchical structures. The leaf-like cobalt possessed hexagonal close-packed (HCP) phase structure. The hierarchical leaf-like cobalt exhibited high saturation magnetization (M_s) of 151.6 emu/g and coercivity (H_c) of 158.5 Oe. The low temperature chemical reduction method is quite simple, it will provide possibility for large scale preparation of such leaf-like cobalt. Due to the specific structure and magnetic properties, these cobalt leafs are expected to have potential applications as candidates for microwave absorption and sensors.     

Magnetically stabilized fluidization of a mixture of magnetic and non-magnetic particles in a transverse magnetic field

This paper presents an investigation of the hydrodynamic behavior of a gas-solid magnetically stabilized fluidized bed. It consists of a mixture of spherical steel particles with glass balls subjected to a magnetic field, transverse to the gas flow, which is created by two permanent magnets. Pressure drop, bed stability and expansion are studied. A data correlation in good agreement with experimental results was developed. It takes into account the modification of the bed structure in the presence of two types of particles: steel particles forming chains following the field lines and considered as “pseudo-plate” particles and non-aggregated non-magnetic particles.     

水中二氧化硅分析方法的改进

分析了传统的二氧化硅分析方法--目视比色法存在的缺陷,提出了准确测定水中二氧化硅的新方法--钼蓝比色法.结果表明,该法准确可靠,方便快捷.     

磷矿石中氧化铝含量测定方法优化

偏铝酸盐分离-EDTA容量法测定磷矿样品氧化铝含量,熔样和杂质分离一次完成,操作方法简单,分离效果好,但熔样过程难以精准控制,进而导致测定结果不稳定。对熔样操作步骤进行优化后,测定误差小,能更准确地分析磷矿样品中氧化铝的含量,有效提高分析质量,为磷矿有效综合利用提供准确的基础数据。     

Changes in the nanoparticle aggregation rate due to the additional effect of electrostatic and magnetic forces on mass transport coefficients

The need may arise to be able to simulate the migration of groundwater nanoparticles through the ground. Transportation velocities of nanoparticles are different from that of water and depend on many processes that occur during migration. Unstable nanoparticles, such as zero-valent iron nanoparticles, are especially slowed down by aggregation between them. The aggregation occurs when attracting forces outweigh repulsive forces between the particles. In the case of iron nanoparticles that are used for remediation, magnetic forces between particles contribute to attractive forces and nanoparticles aggregate rapidly. This paper describes the addition of attractive magnetic forces and repulsive electrostatic forces between particles (by ‘particle’, we mean both single nanoparticles and created aggregates) into a basic model of aggregation which is commonly used. This model is created on the basis of the flow of particles in the proximity of observed particles that gives the rate of aggregation of the observed particle. By using a limit distance that has been described in our previous work, the flow of particles around one particle is observed in larger spacing between the particles. Attractive magnetic forces between particles draw the particles into closer proximity and result in aggregation. This model fits more closely with rapid aggregation which occurs between magnetic nanoparticles.     

比色法测定饮用水中二氧化氯的含量

采用比色法测定饮用水中二氧化氯的含量。该方法适合于质量浓度在0．25mg／L以上的测量,且在该质量浓度以上的测定精度更高,因此适合于饮用水中二氧化氯含量的测定。     

用ICP-AES内标法测定润滑油中磷含量

研究了用等离子发射光谱仪内标法测定润滑油中磷含量的分析方法。通过选择合适的内标物及实验条件,方法的标准偏差为2%,回收率为97%～104%,可以用于测定润滑油中的磷含量。     

Effect of Fe doping on the magnetic properties of PbPdO2 nanograin film fabricated by sol-gel method

The single-phase Fe-doped PbPdO₂ film was prepared using a sol-gel spin-coating method. The film had a nanograin structure consisting of compacted particles with an average crystallization size of about 35.2 nm. Large amount of Pb vacancies were found in the film. The valences of the Pb, Pd and Fe ions of the film were confirmed to be near 2+, 2+ and 3+, respectively. The additional electron provided by Fe³⁺ and the high ionization energy of Fe³⁺ ensure the stability of the valence of doped Fe ions. The measurement of hysteresis loops and the theoretical fitting of the zero-field-cooled and field-cooled magnetization versus temperature curve indicated that the ferromagnetism and the paramagnetism coexist in the Fe-doped PbPdO₂. And the ferromagnetism persisted up to 380 K. A bound magnetic polaron model based on the Pb vacancies, the carriers and the doped Fe ions was utilized to account for the origin of the film's ferromagnetism. The isolated Fe ions or magnetic polarons were believed to be responsible for the paramagnetism in the film.     

3D gel printing of magnetic hydrogel scaffolds assisted by in-situ gelation in a water level-controlled crosslinker bath

Polyvinylalcohol/chitosan (PVA/CS) is an excellent dual-network hydrogel material, but some significant challenges remain in fabricating composites with specific structures. In this study, 3D gel printing (3DGP) combined with a water-level controlled crosslinker bath was proposed for the rapid in-situ prototyping of PVA/CS/Fe₃O₄ magnetic hydrogel scaffolds. Specifically, the PVA/CS/Fe₃O₄ hydrogels were extruded into the crosslinker water to achieve rapid in-situ gelation, improving the printability of hydrogel scaffolds. The effect of the PVA/CS ratio on the rheological and mechanical properties of dual-network magnetic hydrogels was evaluated. The printing parameters were systematically optimized to facilitate the coordination between the crosslinking water bath and printer. The different crosslinking water baths were investigated to improve the printability of PVA/CS/Fe₃O₄ hydrogels. The results showed that the printability of the sodium hydroxide (NaOH) crosslinker was significantly better than that of sodium tripolyphosphate (TPP). The magnetic hydrogels (PVA: CS= 1: 1) crosslinked by NaOH had better compressive strength, swelling rate, and saturation magnetization of 1.17 MPa, 92.43%, and 22.19 emu/g, respectively. The MC3T3-E1 cell culture results showed that the PVA/CS/Fe₃O₄ scaffolds promoted cell adhesion and proliferation, and the scaffolds crosslinked by NaOH had superior cytocompatibility. 3DGP combined with a water-level controlled crosslinker bath offers a promising approach to preparing magnetic hydrogel materials.     

A new method to determine monomer concentration in the polymer particles of emulsion polymerization systems by dynamic light scattering

Emulsifier‐free emulsion polymerization of styrene was performed in the presence of small amount of methacrylic and itaconic acids as carboxylic acid monomers and potassium persulfate as an initiator at 70°C to prepare monodisperse polymer particles. Diameter of monomer swollen polymer particles (d_pswol) was measured by dynamic light scattering for samples taken from the reaction mixture during the Intervals II and III of the emulsion polymerization. Graphically treatment of d_pswol versus conversion data allowed us for the first time to directly determine the critical monomer conversion (x_c), from which constant monomer concentration in the polymer particles (C_MP) during the Interval II was then calculated. x_c and C_MP were obtained to be 0.379 and 5.68, respectively. C_MP value is in good agreement with that obtained by centrifugation method and those reported in the literature for the similar system. Attempts were also made to evaluate the average number of growing chain per particle ( ) during the Interval II of emulsion polymerization of styrene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A new method to determine monomer concentration in the polymer particles of emulsion polymerization systems by dynamic light scattering

In the published article cited above, by considering corrections made on the eq. (19) which will be discussed in the next section, Figure 6 should be replaced with a following new Figure 1. Hence, and values of 0.379 and 5.68 mol.dm^?3, respectively, on pages 1055, 1061, and 1062 should be changed to their accurate values of 0.426 and 5.29 mol.dm^?3, respectively.     

Effect of gravity in differential mobility analysers. A new method to determine the density and mass of aerosol particles

Mobility analysers select particles according to their electrical mobility. In order to take into account the effect of gravity in these analysers, we introduce the settling velocity in equations governing the behaviour of particles. We deduce a new transfer function taking into account the effect of gravity. Based on these theoretical results, we developed a new application. By simultaneously measuring the relaxation time and the electrical mobility of aerosols, we determine their diameter, their mass and therefore their density. In order to validate this theory, we measure the mass of a latex particle (diameter between 0.1 and 2 μm) with a radial flow differential mobility analyser known under the name SMEC. The agreement between the theoretical and the experimental values is good and the uncertainty less than 5% for latex particles with a diameter greater than 0.5 μm.     

On the use of graphical method to determine the targets of single-contaminant regeneration recycling water systems

Water system integration with regeneration recycling can reduce freshwater consumption and wastewater discharge to the maximum extent. In this paper, by analyzing the limiting composite curve of a single-contaminant water system, a method is proposed to construct the optimal water supply line for regeneration recycling. Accordingly the targets for regeneration recycling water systems are obtained. The targets in sequence are the minimum freshwater consumption (the minimum wastewater discharge), the minimum regenerated water flowrate, and the optimal regeneration concentration. The post-regeneration concentration is taken to be fixed in the sequential targeting procedure. The interactions of these targets are analyzed, and formulas for calculating these targets are proposed. The results show that for a single-contaminant regeneration recycling water system, the minimum freshwater consumption is determined by the shape of the limiting composite curve below the post-regeneration concentration. The optimal regeneration concentration is defined as the minimum regeneration concentration at the minimum freshwater consumption and the corresponding minimum regenerated water flowrate. The minimum regenerated water flowrate and the optimal regeneration concentration are both related to the geometrical features of the limiting composite curve of the water-using system and to the post-regeneration concentration. The optimal regeneration concentration has no direct relationship with the pinch concentration.     

Magnesium ferrite nanoparticles as a magnetic sorbent for the removal of Mn2+, Co2+, Ni2+ and Cu2+ from aqueous solution

The aim of this research was to prepare magnesium ferrite (MgFe₂O₄) magnetic nanoparticles and to investigate their sorption characteristics towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions in aqueous solution. MgFe₂O₄ was synthesized by glycine-nitrate combustion method and was characterized by low crystallinity with crystallite size of 8.2?nm, particle aggregates of 13–25?nm, BET surface area of 14?m²/g and pore size of 8.0?nm. Sorption properties of MgFe₂O₄ towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions were studied using one-component model solutions and found to be dependent on metal ions concentration, contact time, pH and conditions of regeneration experiment. The highest sorption capacity of MgFe₂O₄ was detected towards Co²⁺ (2.30?mmol?g¹) and Mn²⁺ (1.56?mmol?g^?1) and the lowest towards Ni²⁺ (0.89?mmol?g^?1) and Cu²⁺ (0.46?mmol?g^?1). It was observed that sorption equilibrium occurs very quickly within 20–60?min. The pH_zpc of sorbent was calculated to be 6.58. At studied pH interval (3.0–7.0) the sorption capacity of MgFe₂O₄ was not significantly affected. Regeneration study showed that the metal loaded sorbent could be regenerated by aqueous solution of 10^?3 M MgCl₂ at pH 6.0 within 120?min of contact time. Regeneration test suggested that MgFe₂O₄ magnetic sorbent can be efficiently used at least for four adsorption-desorption cycles. The high sorption properties and kinetics of toxic metal ion sorption indicates good prospects of developed sorbent in practice for wastewater treatment.     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.     

Application of fractional calculus to the modeling of the complex magnetic susceptibility for polymeric‐magnetic nanocomposites dispersed into a liquid media

The objective of the present work is to develop a fractional model which describe in a precisely manner the real and imaginary parts of the complex magnetic susceptibility for polymer‐magnetic nanocomposites dispersed into a liquid media, using differential and/or integral operators of fractional order (fractional calculus). The theoretical results show that the shape of the curves of both real and imaginary parts is depending of the fractional order of this new model named Fractional Magnetic Model (FMM). Moreover, the comparison between theoretical and experimental results show that the FMM describe quite well the complex susceptibility response of the polymeric systems containing magnetic nanoparticles at low frequencies (from 0.1 to 10⁵ Hz). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009